An instrument which indicates the presence of dust particles in the atmosphere. Also spelled coniscope.

A weakly colored lunar halo identical in form and optical origin to the solar parhelion.

A method of winds aloft observation in which the elevation and azimuth angles of a theodolite are read while visually tracking a pilot balloon. Balloon height data is estimated from assumed balloon ascension rates.

A clock-driven instrument mounting which automatically and continuously points in the direction of the sun. It is used with a pyrheliometera,hen continuous direct solar radiation measurements are required.

A photometer which measures the intensity of radiation as a function of the frequency (or wavelength) of the radiation.

A type of climatic diagram whose coordinates are some form of temperature vs. a form of humidity or precipitation.

A curve showing the variation of temperature with height in the free air. See lapse rate.

Wind with a speed below 1 knot (1 mph); Beaufort scale number 0.

An inert gas. A colorless, monatomic element which is found to occur in dry air to the extent of only 0.000524 percent by volume. Helium is very light, having a molecular weight of only 4.003 and specific gravity referred to air of 0.138. Because helium i ...

An ion counter of the aspiration condenser type, used for the measurement of the concentration and mobility of small ions in the atmosphere.

A cone-tipped metal rod designed to be driven downward into deposited snow or firn. The measured amount of force required to drive the rod a given distance is an indication of the physical properties of the snow or firn.

See calorie.

An instrument for determining the degree of polarization of light. See photopolarimeter.

An instrument for determining the direction of cloud motion. There are two basic designs of nephoscope, the directvision nephoscope and the mirror nephoscope.

A liquid-in-glass or liquid-in-metal thermometer using mercury as the liquid.

in United States weather observing practice, the highest "instantaneous" wind speed recorded at a station during a specified period, usually the 24-hour observation day. Therefore, a peak gust need not be a true gust of wind.

A temperature scale with the ice point at 273 degrees and boiling point of water at 373 degrees. It is intended to approximate the Kelvin temperature scale with sufficient accuracy for many sciences, notably meteorology.

The ratio of the amount of electromagnetic radiation reflected by a body to the amount incipient upon it, commonly expressed as a percentage. The albedo is to be distinguished from the reflectivity, which refers to one specific wavelength.

Instrument used to measure the amount of water evaporated from the soil surface during a given time interval.

A measure of long-term precipitation effectiveness. The ratio of the normal annual rainfall to the normal annual evaporation.